I have recently replastered a fire place wall as it was slightly damp for about 12-18 inch above skirting. I was advised restoration plaster would be suffice, however after putting lining paper on the wall the problem seems to be still there. I have given the wall a full week to dry which I thought would have been long enough. This is only a problem on the front wall of the fireplace, the side walls are fine. Have I given the plaster long enough to dry? Should I consider drilling a new DPC into the front wall of the fireplace?
Water can still come down the chimney after the fireplace has been bricked up.
Is there a ventilator fitted to allow air circulation?
If not there should be and you'll propably find that the problem disappears once it has dried out.
The DPC should be well BELOW the level of the fireplace - however if the void is filled and bridges the DPC then damp will rise from below. In that case you need to lower the level of the infill to below the DPC level. And still fit a ventilator.